1. Field of the Invention
This invention relates to a treatment object conveyor apparatus for conveying objects to be treated inside a chamber, a semiconductor manufacturing apparatus comprising the treatment object conveyor apparatus, and a treatment object treatment method that uses the semiconductor manufacturing apparatus.
2. Description of the Related Art
In FIG. 8A-FIG. 8D are diagrammed a treatment object conveyor apparatus for conveying objects to be treated, which configures a main component of a conventional semiconductor manufacturing apparatus. A vacuum chamber comprises an upright vacuum chamber 1, and, above and below, two connecting chambers 2 and 3 that are connected laterally, so that a treatment object 4 such as a semiconductor wafer or a wafer cassette for holding semiconductor wafers can be conveyed between the vacuum chamber 1 and the connecting chambers 2 and 3. FIG. 8A is a front elevation diagramming how conveying is done in the horizontal direction indicated by arrow B between the vacuum chamber 1 and the upper connecting chamber 2. FIG. 8B is a side elevation of FIG. 8A. FIG. 8C is a front elevation diagramming how conveying is done in the vertical direction indicated by arrow A inside the vacuum chamber 1. And FIG. 8D is a front elevation diagramming how conveying is done in the horizontal direction indicated by arrow B between the vacuum chamber 1 and the lower connecting chamber 3.
An elevator mechanism 16 that raises and lowers a treatment object conveyor robot 12 is deployed inside the vacuum chamber 1. To describe the configuration of this elevator mechanism 16, a straight guide shaft 7 and a threaded shaft 6 are deployed upright between two elevator attachment bases 5 and 6 located at the top and bottom inside the vacuum chamber 1. To the threaded shaft 8 is attached an elevator pedestal 9 that ascends and descends along the guide shaft 7. For this reason, a threaded hole that engages the threaded shaft 8 and a guide hole in which the guide shaft 7 can slide are provided in the elevator pedestal 9. By engaging the elevator pedestal 9 with the threaded shaft 8 and turning the threaded shaft 8, the elevator pedestal 9 is made to ascend and descend along the guide shaft 7. A motor 10 that is designed for operation in air and that is the drive source for turning the threaded shaft 8 is provided in the atmosphere outside the vacuum chamber 1. This is because motors designed for use in a vacuum are expensive. The turning shaft of the motor 10 penetrates to the inside of the vacuum chamber 1 via a magnetic seal 11, and is linked to the threaded shaft 8 through the elevator attachment base 5, so that the turning thereof is transmitted to the threaded shaft 8.
With only the elevator pedestal 9, the treatment object 4 can only be made to ascend and descend in the vertical direction (arrow A), wherefore the elevator pedestal 9 is linked to a treatment object conveyor robot 12 to achieve complex movements of the treatment object 4 that include movements in the horizontal direction (arrow B). The treatment object conveyor robot 12 comprises a conveyor arm 13 and a drive unit 14 comprising a motor. The conveyor arm 13 is turned or extended and retracted by the drive unit 14 to convey the wafer-holding wafer cassette or other treatment object 4 in the horizontal direction.
Unless the entire treatment object conveyor robot 12 is made to ascend and descend, it is possible to place the drive unit for the treatment object conveyor robot 12 outside of the vacuum chamber 1. However, in order to cause the entire treatment object conveyor robot 12 to ascend and descend, the drive unit 14 is accommodated inside an airtight vessel 15 from which communication with the outside has been cut off, thus preventing dust generated in conjunction with the movement of the drive unit 14 from being scattered inside the vacuum chamber 1. For the same reason as that stated earlier, designing the drive unit 14 to operate in a vacuum results in high cost, wherefore an inexpensive drive unit designed for use in air is used, with the interior of the airtight vessel 15 normally at atmospheric pressure.
The treatment object conveyor apparatus described in the foregoing is subject, however, to the following problems.
(1) The elevator mechanism comprising such sliding parts as the guide shaft 7, threaded shaft 8, and elevator pedestal 9, etc., is deployed inside the vacuum chamber 1, wherefore particles and the like are produced by the sliding parts and not only constitute a danger of contaminating the clean environment inside the vacuum chamber 1 but also result in a larger vacuum chamber 1 because the elevator mechanism 16 is inside the vacuum chamber 1.
(2) The drive unit 14 inside the airtight vessel 15 linked to the elevator pedestal 9 is designed for operation in air, wherefore, if a leak develops in the airtight vessel 15 so that the interior thereof becomes a vacuum as inside the vacuum chamber 1, there is a danger that the drive unit 14 which is designed for operation in air will be damaged so that stable operation cannot be obtained. In order to prevent this, the drive unit 14 must be designed to operate in a vacuum, which makes it expensive.